Provided are a memory package, an expansion memory module, and a multi-module memory system. A base memory module, to/from which an expansion memory module is capable of being attached/detached, includes a module board, a plurality of module terminals arranged on the module board to be connected to a slot, and a plurality of memory packages, each of which including a first surface to be attached to the module board and a second surface opposite to the first surface facing away from the module board, wherein each of the plurality of memory packages includes a plurality of package terminals exposed on the second surface of the memory package to be connected to the expansion memory module.